The invention relates to a brake and control apparatus for the opening of a brake primarily for a winch and more particularly but not exclusively for a lifting winch controlled hydraulically.
For this hydraulic control it is known to utilize a pump, generally of variable flow, feeding a motor whose shaft is connected in rotation directly or through a reduction means to the control shaft of a winch.
In the case of a lifting winch, the action of the weight of the suspended charge naturally tends to cause the descent of the charge and because of this to cause rotation in the corresponding direction of the motor shaft until the flow form the pump is sufficient to compensate for the losses of the circuit.
Also, in view of the blocking of the charge at the end of each of its movements of ascent or descent, such a winch is provided with a brake acting on a piece connected in rotation with the winch.
When after such a blocking of the charge the movement to be obtained is a descent, the weight acting in the same direction as this movement, the brake can, without inconvenience, be opened before the motor is sufficiently fed, for, if necessary, control of this descent.
On the other hand, in the case where the movement to be obtained is an ascent, the weight then acts in the opposite sense to the movement and should the opening of the brake occur only a short time before the motor provides the necessary couple to counterbalance the charge, a harmful blow to the winch could occur and to its charge by causing a free fall before the ascent.
From this fact, it is indispensable, at least for the ascent movements of the charge, to provide control apparatus of the opening of the brake which permits this opening only upon equilibrium of the charge by the motorcouple and, in the case of hydraulic control, upon a sufficient flow from the pump.
To obtain this result, it is known to place in opposition on the same "piece" two couples of rotation comprising:
ONE COUPLE, OBVIOUSLY, CREATED BY THE TRACTION OF THE CHARGE TO BE BALANCED; AND
THE OTHER COUPLE, BY THE FORCE OF A DIRECT ACTION JACK THE CHAMBER OF WHICH IS IN COMMUNICATION WITH THE FEED CIRCUIT OF THE MOTOR.
The "piece" thus subjected to these two couples then provides a balance which rotates in one direction by compressing the chamber of the jack when the couple of the charge is greater and thus primarily at the end of each movement and then in the reverse direction under the action of the jack as soon as the pressure in the chamber of the jack passes the equilibrium point of the charge.
It is then sufficient, during the course of displacement of the "piece" and of its jack, to act directly or indirectly through one of these elements on a contact or control valve controlling the opening of the brake.
To make up this "piece" it is known to utilize the support of the control elements of the winch such as the motor, reduction gear, or brake and to mount this support in such a way that it can oscillate around the axis of the winch under the action of the rotational couple due to the charge while compressing the direct action jack which connects the support to a fixed point.
This construction requires the rotation of a large mass of the support and of the control elements for the winch, implicitly and unfortunately requiring an enlarging of the elements and primarily of the jack and causes a certain delay in the functioning.
In an attempt to correct these inconveniences in another embodiment, the "piece" is limited to the support of those of the elements of the brake which normally are associated with a fixed base and this support is, with respect to the fixed base carrying the winch, mounted freely in rotation in the limits of extension and compression of the jack referred to above.
This jack, which, in accordance with the construction of known devices, is an essential element to control the opening of the brake, greatly increases the cost of the construction and limits the application of such apparatus to a brake for a winch controlled hydraulically.